This invention relates to a numerical control system and, more particularly, to a numerical control system in which a single automatic programmer is connected to a plurality of numerical control devices.
Numerical control devices include so-called manual numerical control devices which are comparatively simple in construction and do not rely upon a tape reader for reading in data. In one configuration of a manual numerical control (or NC) device, data such as positioning or cutting data is preset on a number of dials provided on the panel of the NC device which, subsequently, reads the data from the dials in sequential fashion to execute the prescribed numerical control processing. Alternatively, the numerical data may be entered successively and stored in a memory from an MDI (manual data input unit), after which the NC device sequentially reads the numerical data out of the memory to perform the desired numerical control processing. Thus, with a manual NC, (1) direct programming is performed at the job site while the technician/programmer observes the work drawing or blueprint, (2) the program data is entered by means of the dials or MDI, and (3) the manual NC causes the machine tool to perform an actual machining operation on the basis of the program data.
The early manual NC devices of the above type did not lend themselves to easy programming, machining efficiency was poor because of the considerable time required for programming, and input errors were quite common. Improved manual NC devices have appeared which make it possible to carry out programming directly from blueprints, in a shorter period of time, and with fewer errors. Nevertheless, even these devices do not enable programming to be performed rapidly, despite the improvement over the earlier devices in terms of the programming time requirement. In addition, with the manual NC devices proposed heretofore, control of the machine tool cannot be performed while programming is in progress. This is a serious disadvantage since the prolonged machine tool idle time results in reduced efficiency. In an effort to solve these problems, a manual NC device has been developed which incorporates separate hardware (such as a microprocessor exclusively for preparing the machining program, and hardware (again, such as a microprocessor) exclusively for controlling the machine tool. These separate items of hardware operate independently of each other, with the arrangement being such that the completed machining program is transferred from the storage area on the programming side to the storage area on the machine control side whenever necessary. It is therefore possible to realize rapid programming and to control the machine tool even while programming is in progress. This recently developed manual NC device thus functions as both an automatic programmer and numerical control device and is advantageous as it greatly shortens programming time and enhances efficiency by permitting numerical control to be carried out while a program is being prepared. A problem encountered with this latter manual NC device is one of total cost, since additional expenses are entailed by providing each of the NC devices at a factory with the automatic programming function. Furthermore, while the above manual NC device does have the advantage of enabling programming during the control of a machine tool, such programming must be carried out at the location of the NC device, namely at the job site, where the noisy environment can be a disturbing factor.